The objective of this investigation is to develop a new technique for visually mapping the distribution of the opiate receptors on the cell body and/or neurities of the single amygdaloid neuron, and to examine the structure of the methionine-enkephalin pentapeptide and the opiate agonist receptor site via biophysical cytochemistry. These goals may be acheived by labelling the methionine-enkephaline with a fluorescent probe. Reacting dansyl chloride (the dansyl group acts as a fluorescent molecular probe) with the unprotonated amino terminal of enkephalin will yield dansyl enkephalin. The fluoresence characteristics (lambda, tau, I) of N-dansyl-enkephalin will be examined in solution and the presence of the opiate receptors on fixed cultured nerve cells. The single cells will be taken from the amygdaloid nuclear complex of 15 days old albino rats and maintained in a dissociated cell culture; and, in presence of dansyl endephalin, their fluorescence emission will be analyzed by microspectrofluorometry; the amygdaloid nuclear complex has been shown to have a larqe quantity of opiate receptor binding activity and to involved in the behavioral aspects of pain. The stereospecific binding of N-dansyl-enkephalin3 to the opiate receptor will be assessed by its relative ability to inhibit the binding of H-met-enkephalin to membrane fragments of rat brain, as compared to the opiate receptor binding of non-labeled enkephalin.